Goubou line, "G-line" (was Tesla Coil RF Transmitter)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: William Beaty <billb@xxxxxxxxxx>

On Sun, 11 Sep 2005, Tesla list wrote:

> Original poster: Ed Phillips <evp@xxxxxxxxxxx>
>
> 3 -- given the above statements, why is it so hard for anyone to
> believe that Tesla was transmitting by conduction through the earth,
> and not propagation through the air?! Just becuase you CAN transmit
> RF through the air, doesn't mean it is the ONLY way to do it."

This isn't quite correct.  RF energy cannot flow through conductors.
After all, whenever we send electrical energy down a piece of coax or a
length of lampcord, both the coax and the lampcord function as waveguides,
and the electromagnetic energy is flowing through the space outside the
metal and not flowing inside the conductors.  The current is in the metal,
yet the flowing energy is in the space nearby.

If Tesla successfully used the Earth to transmit VLF energy from place to
place, the energy had to have flowed through the air, not through the
Earth.  Yes, the EM energy was associated with electric currents in the
Earth's surface.  And the EM energy would be constrained to follow the
Earth's surface.  But electrical energy doesn't move through conductors.
Look at microwave waveguides (the hollow rectangular type), where the
currents are in the metal surface, while the RF energy is in the hollow
center of the pipe.  Coax and twinlead are similar, and they still behave
as waveguides regardlesss of frequency.

Or in other words, *ALL* electrical energy is the same thing as "radio
waves."  Electrical technology is all based on propagating EM fields
guided by electric circuits.  The only difference is in our minds:  when
electromagnetism is guided by some wires, we concentrate on the currents
in the wires, ignore the surrounding field, and we call it "electrical
energy." But when it flys off an antenna and crosses empty space, we call
it "radio waves."  Yet the energy is made of space-filling EM fields in
either case.  Similarly, the only difference between a power supply and a
radio transmitter is...  the radio transmitter is connected to an antenna.
So Tesla's system was using the Earth as a waveguide in somewhat the same
way that the electric utility companies use copper wire as waveguides.


Here's where it gets weird.  Perhaps Tesla's system did not actually take
advantage of the Ionosphere at all.  After all, in the microwave waveguide
system called the "Goubou Line" or "G-line," there is an electric current
in a single conductor, and the EM waves are guided by that conductor.  A
"G-line" system is fed by conventional coax cable, but then the coax
shield is flared out into a horn shape called the Launcher, and the center
conductor continues on alone.  At the far end is another "horn," the
Catcher, which leads to the shield of normal coax.  In between the horns
the single wire has no return path, just as there is no return path in
optical fibers or in rectangular microwave waveguides.  Or, from an
e-field standpoint, the single wire functions as it's own return path,
since the fast-moving regions of positive and negative charge on the long
"G-line" wire are connected together by electric field lines.

An analogy:  if electric circuits are like drive belts wrapped around
pulleys, then Tesla's system was sending sound waves along a single length
of stretched rope.  When frequency is high, no closed circuit or return
rope is neeed.

If Tesla's system is similar to microwave G-line, then the Earth's
ionosphere plays a less significant role, since the single conductor
itself is the only necessary part.  But in that case, the "launching horn"
is the important part.  The smaller the horn, the worse the impedance
match, and the harder it becomes to send electrical energy along the
single wire.


Hmmm, I wonder what happens if we actually try sending signals along a
couple hundred feel of coax cable, but we strip off the shield braid in a
fifty-foot length in the middle of the cable?  Well, I guess it would only
be a fair test if we used 100MHz signals or higher, so 50ft is many
wavelengths long.  Also use ungrounded signal generator and detector, so
there's no earth-return path.  Could we light a light bulb over such a
transmission line?  (Of course put a tank circuit on the light bulb to
take advantage of resonant matching effects.)



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William J. Beaty                            SCIENCE HOBBYIST website
billb at amasci com                         http://amasci.com
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